DEPRESSED GROWTH-RATE AND DAMAGE TO THE CARTILAGE OF RED-SEA BREAM LARVAE ASSOCIATED WITH EXPOSURE TO AMMONIA

A depressed growth rate in the absence of pathological changes was obs erved in the larvae of a marine teleost, red sea bream Pagrus major, e xposed to 0.002 and 0.02 mg/l NH3-N (non-ionized ammonia) for 72 hours . Such levels of ammonia are frequently encountered in practical larva l culture facilities in Japan and may have a detrimental effect on pro duction. In a second experiment a histological study revealed that thr ee-day-old larvae exposed to 0.05, 0.08, and 0.15 mg/l NH3-N for 24 ho urs developed cytoplasmic vacuoles in the chondrocytes. The possible c auses of such pathology and its relationship to the observed depressio n in the growth rate are discussed.